


Arcobaleno Cielo

by qmzr



Series: Discard Pile? [2]
Category: Katekyou Hitman Reborn!
Genre: Gen, I wonder what sort of trauma he got from watching his mentor die but i didn't elaborate on that, except he's an arcobaleno now, my poor boy is more confused than ever, this is sort of your basic dragged back in time fic i guess?
Language: English
Status: In-Progress
Published: 2019-10-16
Updated: 2019-10-16
Packaged: 2020-12-17 17:42:41
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 3,414
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21058397
Author URL: https://archiveofourown.org/users/qmzr/pseuds/qmzr
Summary: Years after Kawahira chose the new generation of Arcobaleno, Tsuna continued with his life and became the first Vongola boss to be one of the strongest seven. It wasn't all smooth sailing, but he slowly began to regain the reputation lost since Primo's time. However, on a rare free day off, Tsuna inexplicably blacks out and wakes up to see his younger, uncursed self standing over him.





	1. Chapter 1

**Author's Note:**

> This is an old fic that I originally put up on ffn.net like two years ago under the alias of "Ailiac" and was actually the first work that I had ever posted online, so forgive anything that sounds kind of odd. However, my dedication to finishing it waned quickly and I didn't get very far.
> 
> ***(aka if you want to adopt it or something, I'd be happy to hand you the reins since I'm not going to do more with it)

“Dame-Tsuna, you got thirty two out of forty of these these wrong. Do it all over.”

Tsuna stared at Reborn with a mixture of despair, shock and mutiny. He had been working on it for the past two hours! He heard a clicking sound and turned to face a gun aimed at his forehead. That was enough to shatter any possible escape plans.

Reborn smirked knowingly, making Tsuna sign in resignation. Before he could restart, though, a loud explosion rocked the house. Dashing to the window, Tsuna barely caught sight of bright orange light before it receded, revealing a small body. It was too dark to tell the details, but it wasn't moving. Was it dead?

Suddenly, Reborn landed on his shoulder with an odd glint in his eyes. “What are you waiting for? Go take a look.”

Tsuna looked at him fearfully and said, “But what if it's dangerous? We don't know what it is!”

Reborn stared at Tsuna unblinkingly. After an uncomfortably long silence, he cracked under the pressure and exclaimed, “Ok, ok, I'll go!”

He stumbled down the stairs and opened the door. His mom glanced at him with a bright, clueless smile, but didn't say anything. Reborn waved at her and told Tsuna to hurry up.

As he approached the body, it came into clearer focus. The baby had wild brown hair and was dressed in a hoodie. Clutched in his hand was an odd orange box, and several similar ones were attached to his belt. However, the most prominent thing about this infant was as slight, still fading glow coming from…. a pacifier?

“I knew that light looked familiar.” remarked Reborn, frowning. 

Tsuna looked at him quizzically. “Is that an Arcobaleno?” he asked.

Without turning away from the unnamed infant, he replied, “He is. The questions now are who and why. The current sky Arcobaleno is supposed to be the boss of the Giglio Nero Famiglia.”

The unnamed infant twitched in discomfort. A small, fuzzy chipmunk suddenly emerged from his pocket and crawled to his face, poking its nose at his cheek worriedly. It then stared at Tsuna and Reborn expectantly, as if it were trusting them to help.

“Well?” prompted Reborn, heeding its gaze. “Take him inside. He clearly needs to rest, and outside on the ground isn't a good place for that.”

Tsuna looked at him disbelievingly. “Ehh!? We don't even know him! What if he's dangerous!”

“Do it or consider your workload doubled.” Uncharacteristically, no smirk crossed Reborn's face as watched as his pupil grimace.

As Tsuna picked him up, the Arcobaleno twitched again, stronger this time. His brown eyes flitted open, staring ahead blankly. Seconds later, they were sealed shut once more.

****

It was dark, the sort of suffocating darkness that pressured you on all sides. It was here that a orange light flickered to life, borne from a radiant flame atop the head of a brown-haired boy. 

He forced down his ringing premonitions, and studied his surroundings. It was completely empty, save for the sleek black floor.

Suddenly, he spun around, noticing colorful lights behind him. There, as if they simply materialized from nowhere, the Arcobaleno stood motionless, their pacifiers glowing brighter by the second. Then, just as suddenly, six of them were reduced to the damaged, grotesque, bodies of the once-Arcobaleno. Their lights were extinguished.

Tsuna gasped and collapsed in shock as he watched the bodies decay in fast-forward. No matter how much he desperately wanted to turn away, his body refused to listen.

One last yellow glow remained. Reborn walked up to Tsuna, face shadowed by the brim of his hat.

“Tsuna.” He tilted his hat up, revealing an genial, unforced grin. “Thank you for being my student.”

He pIcked off his hat and placed it gently on Tsuna’s head. “And goodbye.” 

With that, his pacifier went out. The sky flame followed as well. It fizzled out, leaving only the behind darkness behind. He could feel himself sinking and shrinking until-

_ “No!”  _

Tsuna eyes flew open and he shot up, slamming his head on something hard.

“Ow!” Two cries filled the air as one head collided with another. 

Tsuna recovered first and stared, eyes wide, at the taller figure, who was still wincing when he opened his eyes.

“Oww… why does this always happen to me?” He complained. 

Tsuna, who looked like he had been frozen, had his eyes locked on him. 

“Why are you looking at me like that?”

Slowly, Tsuna raised his tiny hands and rubbed his eyes. After blinking a few times, realization set in and his eyes began to dilate. “Y-you.. you're..?” he sputtered.

The voice of an infant drew their attention away. “What do you mean by that, sky Arcobaleno?” His tone was somewhat wary, but not unfriendly. Nevertheless, Tsuna’s gaze snapped onto him.

It was silent for a few seconds before Reborn warned, “Don't even try to lie. I can tell. Who are you?”

Tsuna blinked, and with the steadiest voice he could muster, responded. “Tsunayoshi Sawada.”

Reborn's eyes widened. Marginally, perhaps, but it was still there. It was the mark of a professional that he regained his composure so quickly. Redirecting the conversation, he said, “What should we call you? It'll be inconvenient if you were both referred to as Tsuna.”

Tsuna responded in kind. “Naturally, it should be me who goes by a nickname. How about Cielo? It’s simple and self-explanatory.”

“Sky? It's a bit uncreative, but that doesn't matter.” said Reborn. “Tsuna, meet our new roommate.”

Tsuna, who hadn't uttered a word during the exchange, looked up. In a slightly indignant tone, he said, “Do I even get a say? It's my room!”

Needless to say, he immediately began shrieking when he saw Leon morph into a gun.


	2. Chapter 2

As Tsuna attempted to protect his breakfast from Reborn and Lambo, Cielo ruminated on his current situation. He didn't let himself show it, but it had been a massive shock to find himself staring at the roof his old bedroom instead of the one at Vongola Mansion. It was only thanks to Lal Mirch that he didn't face-fault and pass out. She had only become a more zealous trainer after recovering from Colonello’s death, which he admitted that had mixed feelings about.

Cielo dodged Lambo’s grenade by a hair as it whizzed past and continued his breakfast. Nana, blissfully oblivious as ever, assumed that yet another store was having a sale despite the proximity of the explosion. All seemed to be normal.

Despite the Arcobaleno’s sudden intrusion into their lives, nobody seemed to mind his presence. Reborn just invited Cielo in, having judged him to be no real threat. It was almost unnerving how quickly and confidently he sized Cielo up, but that was only to be expected. On the other hand, Tsuna didn't really seem to believe Cielo’s explanation, but accepted him with the typical show of dismay as he did with every other new “housemate.” 

Lambo, I-Pin, and Fuuta simply saw him as another playmate when Reborn introduced him at the start of breakfast, while Nana happily exclaimed that her family was “growing so fast!”

Lost in thought, Cielo didn't notice a lone chopstick flying directly at his forehead. A sharp “thwack” echoed through the room and pair of hands clutched at the site of the hit. Cielo grumbled inwardly as he turned to face the perpetrator.  _ Did nothing ever change? _

Reborn smirked. “Baka-Cielo, listen when mama is talking.” 

Cielo, having been snapped out of his thoughts, glanced at his mom. Sure enough, it turned out that Nana was fretting about Tsuna's lunch, which he had forgotten on his rush to the door.

“Don't worry, mama.” Reassured Reborn. “Cielo and I will take it to him. Right, Cielo?”

Cielo, knowing that it was futile to resist, sighed and nodded. And so, the pair bid Nana goodbye and set off. Cielo’s chipmunk, Leaf, stuffed a few more almonds into her cheek pouch before taking a running leap onto his head.

As soon as the door shut behind them, Reborn dropped his carefree façade and turned to him. “How and when did you become an Arcobaleno? Where's Checkerface?”

He smiled grimly, having been expecting this. “Sometime within a year, Kawahira, that's Checkerface, will hold the Representative Battle of the Rainbow. He promised that the winner would have their curse removed, but it was all just a ploy to gather new candidates to replace all seven. As for his location-if I knew how to find him, I would've done so years ago.”

Reborn looked at him oddly. “What are you implying? If there's anything I know about both you and Tsuna, it's that neither of you are the sort to seek revenge.”

“What I mean is that there's a chance-”

“For what?”

“-for the curse to be removed with virtually no consequences.”

Reborn instantly went absolutely still. After a short period of silence, he evenly asked, “How solid is the theory?”

“I consulted multiple times with Gokudera, who became an expert in this field, and Talbot. Both seem to hold the belief that it would probably work as long as Bermuda agrees to lend his flames.”

“Who is Bermuda?”

_ Oh yeah, Reborn didn't know about him until the fight against Enma.  _ Taking a deep breath, he asked, “Do you know why the Vindice are always covered in bandages?”

Reborn looked at him quizzically. “Nobody does, except for the Vindice themselves. I assume you’re going to prove that statement wrong?”

Nodding, Ciel elaborated. “All of them are old Arcobaleno who had their flames taken away; their bodies merely grotesque, zombie-like versions of their old adult selves. Their boss, Bermuda von Veckenschtein, however, is still in his infant form and is the lone holder of the flames of night, as well as the clear pacifier.”

Frowning, Reborn intensified his stare. Cielo fought the urge to look away, as they hadn't broken eye contact once since the start of the conversation; the pressure was mounting high. Reborn was on a whole other level from your typical hitman.

“So, you're saying that you know how to safely reverse the curse, and to do it, we have to talk to Talbot and borrow Bermuda’s flames?” repeated Reborn.

Cielo nodded. “And the only reason why we couldn't implement it before the shift happened was due to Kawahira’s disbelief in the plan and Talbot’s late appearance. Later, I even asked Bermuda for his cooperation if we were able to track Kawahira down, which he instantly accepted.”

There was a lull in the exchange while Reborn seemed to think to himself. Out of nowhere, as if a switch was flipped, a sunny smile split Reborn's face. “Great! It's settled then!”

Thrown of by the shift in the atmosphere, Cielo stuttered, “W-what!? But there's so many things that could go wrong! Kawahira might do the same thing as last time! You might-”

“Baka-Cielo shouldn't think too hard,” interrupted Reborn. “The Representative Battle will inevitably happen, right? Why worry about that now? Besides, the biggest problem we currently have is training up dame-Tsuna and “convincing _ ”  _ him to accept the position of Decimo. Will you help?”

With wide, round eyes, Cielo was temporarily struck dumb. Then, he began to giggle uncontrollably, breath hitching slightly.

“Oi, pull yourself together, Cielo. We have to complete our errand,” said Reborn mildly.

After a few more seconds, Cielo managed to return his breathing to normal. “Alright, I got it. Let's go.”

Reborn grinned, but this time, an unpleasant shiver rippled down Cielo’s spine, almost making him cringe. 

“That's more like it.” Reborn turned and began to walk toward Namimori Middle. Cielo blinked and quickly made his way to his side. Did he just imagine it?

“Later, I'd like a little spar to judge your growth.”

Apparently not.

*****

Out of nowhere, Tsuna let out a sneeze. Gokudera, as always, was the first on the case. 

“Tenth! Are you feeling well? Should I escort you to the school clinic?”

Tsuna waved sheepishly. “I’m fine, Gokudera. My nose just itches.”

Somewhat unconvinced, he made a dissatisfied face. Yamamoto simply laughed genially.

Gokudera’s eye twitched. “What's so funny, baseball nut?” he demanded.

Unaware of rising tension, he smiled and said, “Oh, it's nothing.”

“Come on, guys! Lets just go eat.” Tsuna said appeasingly. He reached into his bag and felt around, but after a moment of searching, his panicky smile dropped. 

“Huh? Where's my bento?” he asked confusedly.

Lights flashed in Gokudera’s eyes as he whipped his head to face Tsuna. “Someone must've stolen your mother’s prized cooking! Don't worry, Tenth, I'll teach them a lesson!”

Tsuna's attempt to defuse their daily spat had worked, but only in the sense that the problem had shifted to another direction. He was only beginning to react when he spotted a speck in the sky. Squinting his eyes, he said, “Wait, what is that?”

Yamamoto responded first. “It's too far to tell, but it seems to be coming closer fast.”

Mere seconds passed before added, “Hmm, a mini green hang glider and a small guy in a suit… hey! That's that kid that lives with you, Tsuna!”

Reborn landed and neatly drop-kicked Tsuna into the wall. It took a minute for him to regain his bearings and stand.

“That hurt! What was that for!?” he exclaimed. His indignant expression quickly switched to fear as soon as his tutor gave an innocent smile.

“You forgot the lunch that your mama poured her hard work into. As a punishment, your training will be tripled.”

Tsuna slumped back onto the ground. “No way, that's insane! I can't do that!.”

“Oh, you will. We'll make sure of that.”

Tsuna paused his panicky rant. “We?”

“We.” he repeated

Suddenly, a small flash of orange darted into view and dropped onto the roof. Although disheveled, the infant was breathing evenly and looked none the worse for wear.

“Reborn!” Cielo shouted. “Warn me before you take off like that!”

“This is your new assistant tutor.”


	3. Chapter 3

After getting over the initial shock of Reborn's revelation, everything seemed to proceed as normal (well, after chasing down Gokudera, but that was normal). Nobody, as expected, seemed to heed yet another baby appearing next to Tsuna after lunch, beside the occasional snide remark. As the only sane person, you could practically see the agitated disbelief in his eyes.

When the bell rung to announce the end of class, two babies simultaneously jumped onto Tsuna's shoulders. He looked at them both, then sighed. That prompted a small kick from one of the riders and a shrill “ow!”

When he and the others walked out of the school and onto the streets, everything seemed nice and calm. Gokudera and Yamamoto had stopped quarreling and most were now chattering away with their friends, completely carefree now that school was over. Sadly, amidst all the normality, he spotted an odd glint in his tutor’s eye.

“Tsuna, do you want to go to the nearby forest? Cielo and I will be heading over there for a little while,” he announced.

“Do I even get a choice?” Muttered Tsuna.

“Have you ever?” remarked Reborn. “Now go and switch into hyper dying will form. We should make this quick and head back to mama before she gets worried.”

Forcing down his questions, he grabbed the dying will pills from his pocket and picked two out. Out of the corner of his eye, Tsuna noticed Cielo's expression. He looked vaguely annoyed, as if that kid was being forced to do something, which is something Reborn totally would do. At least neither were alone in their discomfort.

A bright orange flame burst to life and they immediately took to the sky. In no time, they had landed at their destination without a hair out of place. There was a soft thud when two tiny pairs of feet simultaneously hit the ground.

Reborn's eyes locked onto Cielo. “About how strong would you say you are?”

“In my hyper dying will form, I'd say a bit weaker than you,” Responded Cielo. However, without skipping a beat, he added, “If I go into ultimate dying will mode, I can beat you. I'd prefer not to do it too often, though”

As if he expected no less, Reborn grinned and turned to Tsuna, who was staring at Cielo in disbelief. “What about you, then? Could you beat me in a fight?”

He backed away reflexively and babbled, “No way! Why are you asking? You already know that I'm way, way weaker than you! That's impossible!”

A bullet zipped past his head, making him crumple onto the grassy ground. “Shut up, Dame-Tsuna. If Cielo can do it, then you definitely can too.”

He stumbled up and shouted, “What kind of logic is that!?”

“Don't question your tutor,” reprimanded Reborn, his gun glinting threateningly in the sunlight.

Tsuna's mouth snapped shut.

“Ah, good old classic conditioning. Now that that's cleared up, let's start, shall we?” began Reborn. “Cielo, remember?”

Cielo looked at Reborn, expression unreadable. “How could I forget?” he responded, and with that, he closed his eyes. The low sound of air rushing to a lighted flame resounded in his ears as Cielo's eyes opened slowly, revealing his now glowing orange pupils.

Tsuna stared at him in slight bemusement.

“Are you sure we should do it here?” asked Cielo. “We might damage nearby property or alert somebody.”

“I told you, it'll just be a little spar. It won't take long, Baka-Cielo.”

Although Cielo still looked somewhat unconvinced, he duly ignited his fists. Reborn took the cue and his leon-gun. 

What happened next was far too fast for Tsuna to comprehend. There was a loud clash of light and a glimpses of an afterimage. Suddenly, he shrieked as a tree behind him snapped out of nowhere, smoke rising from the damaged trunk. 

The hair on Tsuna's neck stood up.  _ Hiee! They're a hundred times faster than Xanxus! _

They proceeded to tear up their surroundings; the damage accumulating blow by blow. He had yet to even see even one land a clean hit, not that he could, of course. To the untrained eye, they were merely a whirl of color and noise.

Tsuna jumped as he heard them land simultaneously, both breathing only marginally more labored than earlier. They stood there silently, staring into each other's indecipherable eyes.

After a few more tense moments, Reborn dropped his posture. “That's enough.”

“Huh?” said Cielo. “We barely just started.”

“Don't question me, Baka-Cielo. Let's head home.”

A small fizzling sound caught Tsuna's attention as he turned to see Cielo's flame go out. For some reason, Cielo almost seemed to be amused when he heaved a small sigh.

“Okay, I got it. Let's go home.”

* * *

It was dinner time, and Lambo, who was unusually late, had just tottered down the stairs unsteadily in an enormous broccoli costume. Cielo looked up, grabbed his plate, and immediately excused himself from the table.

“Look! Lambo's a big broccoli monster! Hand over all of your food if you wanna live!”

I-Pin gasped. In her hurry to escape, she knocked over her chair, which promptly crashed into the table. Everything probably would've been fine afterwards, had there not been soup bowls, all of which spilled on everyone, except, of course, for Reborn.

Dark energy began to emanate from a corner in the room. “Damn him… this was my newest outfit...” Bianchi muttered. A vein seemed to have popped in her forehead. “Get back here!”

She immediately stood up, whipped a plate of rice cakes from out of nowhere, then dashed out of the room. 

However, she had inexplicably forgotten one on the corner of the table. It quickly melted through the tabletop and down to the leg. Everything fell apart after that, both literally and figuratively.

The unbalanced table toppled over, along with all the dishes on top. Reborn, ever the opportunist, snatched the rest of Tsuna's dinner before it splattered on the ground. He then disappeared in the blink of an eye

Before Tsuna could even protest, a large boom reverberated throughout the house, accompanied by some all too familiar pink smoke. A flash of pink and black flew by as Bianchi chased a screaming “Romeo” with an undying fury. Apparently, nobody told her that you couldn't start a snowball fight without snowballs.

All of a sudden, the sound of an electric crackling made everyone look up. 

There was a translucent, gooey mass of poison cooking stuck to the lights. A second later they all stood in pitch darkness.

All was well.


End file.
